Method and apparatus for synchronizing a wireless network with an external timing source

ABSTRACT

A communications device synchronizes itself with respect to an external reference signal, e.g., a GPS signal. The communications device detects timing reference signals, e.g., beacon signals, from a communications network. If the communications device determines that the network is not synchronized to the external timing reference signal, the communications device operates as a master timing control device. In various embodiments, when operating as a master timing control device the wireless communications device communicates time stamps, e.g., in beacon signals, which indicate a greater passage of time than the actual passage of time. When operating as a master timing control device the communications device transmits network timing reference signals at a higher rate than is being used by the network to seize control of network timing and become the master timing control device. The communications device drives the network timing to synchronize network timing to the external timing reference.

FIELD

Various embodiments relate to wireless communications, and moreparticularly to synchronizing devices in a wireless communicationsnetwork.

BACKGROUND

WiFi chips tend to draw alot of current while in use. This high currentdrain often makes it infeasible to run certain kinds of WiFiapplications on cellular devices. Even though certain power savingfeatures have been proposed, they do not appear to be efficient enoughto run certain WiFi applications on a cellular device even when thedevice is in passive mode without significantly impacting the standbytime. A few examples of such applications include: peer discovery,routing information exchanges, and traffic monitoring.

While synchronizing to a reliable external timing source such as a GPSsignal can facilitate timing synchronization between WiFi devices, allWiFi devices may not be able to receive the external timing signalbecause of their location and/or because they do not include a receivercapable of receiving such a signal. Accordingly, in WiFi systems it isimportant that beacon signaling which is used in the WiFi protocolcontinue to be used between devices to maintain device synchronizationeven if one or more devices are capable of receiving signals from anexternal non-WiFi timing signal source.

Individual devices in WiFi rely on their internal timing clocks tomaintain ongoing timing synchronization to determine the passage of timefrom a point in time where a synchronization operation occurs, e.g.,from a point in time where a timing adjustment is made based on thereceipt of a beacon signal.

It would be desirable if a device with a high degree of timingreliability, e.g., because of its ability to maintain and update itstiming based on a reliable external timing signal such as a GPS signalcould operate as a master device in a WiFi network and control thetiming of the devices in the WiFi network. However, it should beappreciated that a large amount of signaling overhead with regard toestablishing a master/client relationship with regard to timingsynchronization should be avoided if at all possible to allow as much ofthe communication capacity to be used for other functions, e.g., thecommunication of traffic data.

In view of the above discussion, it should be appreciated that there isa need for new and/or improved methods relating to timingsynchronization between devices in a communications network such as aWiFi network. It would be desirable if a device with reliable timingsynchronization could act as a master timing control device but withlittle or no overhead relating to the device explicitly signaling thatit is acting as a master timing control device in the network.

SUMMARY

A communications device which intends to participate in a network, e.g.,an ad-hoc peer to peer wireless communications network, receives anexternal timing reference signal, e.g., a GPS signal, and synchronizesitself with respect to the external reference signal. The communicationsdevice detects timing reference signals, e.g., beacon signals, from oneor more other devices in the communications network. The communicationsdevice makes a determination as to whether or not the network is alreadysynchronized to the external reference. If it is already synchronized tothe external reference, the communications device may join the networkand quickly participate in the network. However, if the communicationsdevice determines that the network is not synchronized to the externaltiming reference signal, the communications device can, and sometimesdoes, operate as a master timing control device. In various embodiments,when operating as a master timing control device the communicationsdevice communicates time stamps, e.g., in beacon signals, which indicatea greater passage of time than the actual passage of time. Whenoperating as a master timing control device the communications devicetransmits network timing reference signals at a higher rate than isbeing used by the network, which is not synchronized to the externalreference, to seize control of network timing and become the mastertiming control device. The communications device drives the networktiming to synchronize network timing to the external timing reference.In some embodiments, once the communications device has synchronizednetwork timing to the external timing reference the communicationsdevice transmits network timing reference signals at a predeterminedrate which is lower than the rate used to drive the network timing tosynchronization with the external reference source.

An exemplary method of operating a communications device correspondingto a communications network, in accordance with some embodiments,comprises: synchronizing to an external timing reference signal from adevice outside said communications network; and operating as a mastertiming control device. In some such embodiments, operating as a mastertiming control device includes transmitting network timing referencesignals, wherein individual successive transmitted network timingreference signals communicate a time stamp that indicates a passage oftime from a preceding network timing reference signal that wastransmitted by the communications device, said indicated passage of timebeing intentionally greater than the actual passage of time.

An exemplary communications device corresponding to a communicationsnetwork, in accordance with some embodiments, comprises at least oneprocessor configured to: synchronize to an external timing referencesignal from a device outside said communications network; and operate asa master timing control device, wherein operating as a master timingcontrol device includes transmitting network timing reference signals,individual successive transmitted network timing reference signalscommunicating a time stamp that indicates a passage of time from apreceding network timing reference signal that was transmitted by thecommunications device, said indicated passage of time beingintentionally greater than the actual passage of time. The exemplarycommunications device further comprises memory coupled to said at leastone processor.

While various embodiments have been discussed in the summary above, itshould be appreciated that not necessarily all embodiments include thesame features and some of the features described above are not necessarybut can be desirable in some embodiments. Numerous additional features,embodiments and benefits of various embodiments are discussed in thedetailed description which follows.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a drawing of an exemplary system in accordance with anexemplary embodiment.

FIG. 2A is a first part of a flowchart of an exemplary method ofoperating a communications device in accordance with various exemplaryembodiments.

FIG. 2B is a second part of a flowchart of an exemplary method ofoperating a communications device in accordance with various exemplaryembodiments.

FIG. 3 is a drawing of an exemplary communications device in accordancewith an exemplary embodiment.

FIG. 4A is a first portion of an assembly of modules which can, and insome embodiments is, used in the exemplary wireless communicationsdevice illustrated in FIG. 3.

FIG. 4B is a second portion of an assembly of modules which can, and insome embodiments is, used in the exemplary wireless communicationsdevice illustrated in FIG. 3.

FIG. 5 illustrates an example in which a wireless communications deviceoperates as a master timing control device and peer to peer wirelesscommunications devices in an ad-hoc network are synchronized with anexternal timing reference signal, e.g., a GPS 1 second signal, via themaster timing control device, thus facilitating the exchange of peerdiscovery signals at a predetermined time interval and facilitatingsleep intervals and power conservation.

FIG. 6 is a drawing illustrating an exemplary wireless communicationsdevice synchronizing with respect to an external timing reference sourcein accordance with an exemplary embodiment.

FIG. 7 is a drawing illustrating an exemplary wireless communicationsdevice detecting network timing signals and determining that the networkis not synchronized to the external timing reference source inaccordance with an exemplary embodiment.

FIG. 8 is a drawing illustrating an exemplary wireless communicationsdevice serving as a master timing control device in which the wirelesscommunications device drives network timing to synchronize to theexternal timing reference in accordance with an exemplary embodiment.

FIG. 9 is a drawing illustrating an exemplary wireless communicationsdevice continuing to serve as a master timing control device after thenetwork timing has been synchronized with respect to the external timingreference in accordance with an exemplary embodiment.

FIG. 10 is a drawing illustrating that an exemplary wirelesscommunications device ceases to operate as a master timing controldevice in response to detecting a loss of synchronization with theexternal timing reference in accordance with an exemplary embodiment.

FIG. 11 illustrates exemplary beacon period timing without a mastertiming control device in accordance with an exemplary embodiment.

FIG. 12 illustrates exemplary master timing control device beacon periodtiming while driving network timing toward synchronization with GPStiming in accordance with an exemplary embodiment.

FIG. 13 illustrates exemplary master timing control device beacon periodtiming after achieving network timing synchronization with GPS timing inaccordance with an exemplary embodiment.

DETAILED DESCRIPTION

FIG. 1 is a drawing of an exemplary system 100 in accordance withvarious exemplary embodiments. Exemplary system 100 includes acommunications network 102, e.g., an ad-hoc peer to peer network 102, aplurality of GPS satellites (GPS satellite 1 116, . . . , GPS satelliteN 118), a ground based GPS repeater 120, a CDMA 2000 base station 122,an eLoran transmitter station 124, a LORAN-C transmitter station 126,and a WWVB transmitter station 128. Each of the devices (satellite 1116, GPS satellite N 118, ground based GPS repeater 120, CDMA 2000 basestation 122, eLoran transmitter station 124, LORAN-C transmitter station126, WWVB transmitter station 128) transmit a timing reference signal(130, 132, 134, 136, 138, 140, 142), respectively. In exemplary system100, there may be, and sometimes are a plurality of communicationsnetworks such as network 102, e.g., ad-hoc peer to peer networks, e.g.,as the wireless communications devices move throughout system 100 andform local networks at different locations which may be separated fromone another.

Exemplary communications network 102 includes a plurality of wirelesscommunications devices with the capability to perform timingsynchronization with respect to an external timing reference signaltransmitted from a device outside the communications network (wirelesscommunications device 1 104, wireless communications device 2 106, . . ., wireless communications device N 108). In some embodiments, differentones of devices (104, 106, . . . , 108) may be able to perform timingsynchronization with respect to different types of external timingsynchronization sources. For example, device 1 104 may be able toperform timing synchronization using any one of signals (130, 132, 134,136, 138, 140, 142), device 2 106 may be able to perform timingsynchronization using any one of signal (130, 132, 134, 136) and deviceN 108 may be able to perform timing synchronization using any one ofsignals (130, 132, 134, 142). A device including the capability totiming synchronize with respect to an external source from outside thenetwork, e.g., wireless communications device 1 104, may, and sometimesdoes act as a master timing control device in network 102. At differentlocations through system 100 one or more or all or none of the differenttypes of external timing signals may be available. In some embodiments,there is a predetermined priority ordering to the external timingsources with regard to which type of source should be used to derivemaster timing control when multiple types of sources are available andthe capability exists to use the multiple available sources. Forexample, in one embodiment the priority ordering, from highest tolowest, is: GPS signals, WWVB signals, CDMA 2000 signals, Loran-Csignals, eLoran signals.

Communications network 102 also includes a plurality of wirelesscommunications devices without the capability to perform timingsynchronization with respect to aN external timing reference signaltransmitted from a device outside the communications network (wirelesscommunications device 1′ 110, wireless communications device 2′ 112, . .. , wireless communications device N′ 114).

FIG. 2, comprising the combination of FIG. 2A and FIG. 2B, is aflowchart 200 of an exemplary method of operating a communicationsdevice corresponding to a communications network, e.g., a communicationsnetwork in which the wireless communications device participates, inaccordance with an exemplary embodiment. The exemplary communicationsdevice implementing the method of flowchart 100 is, e.g., one of thewireless communications deviceS with external source synchronizationcapability (104, 106, . . . , 108) of FIG. 1. Operation starts in step202, where the communications device is powered on and initialized.Operation proceeds from start step 202 to step 204. In step 204 thecommunications device synchronizes to an external timing referencesignal from a device outside the communications network. For example, insome embodiments, the external timing reference signal is a GPS signalfrom a GPS satellite. Other exemplary types of external timing referencesignals which are used, in some embodiments, include, e.g., WWVBsignals, CDMA 2000 signals, Loran-C signals, eLoran signals. Operationproceeds from step 204 to step 206.

In step 206 the communications device monitors to detect network timingreference signals. Step 206 may, and sometimes does, include step 208 inwhich the communications device detects network timing referencesignals. Operation proceeds from step 206 to step 210. In step 210 thecommunications device determines whether or not network timing referencesignals have been detected and controls operation as a function ofwhether or not network timing reference signals have been detected inthe monitoring of step 206.

If network timing reference signals have been detected, then operationproceeds from step 210 to step 212; otherwise operation proceeds fromstep 210 to connecting node A 220. Returning to step 212, in step 212the communications device determines if the communications network issynchronized to said external timing reference signal. Operationproceeds from step 212 to step 214.

In step 214, if the network is already synchronized to said externaltiming reference signal, then operation proceeds from step 214 toconnecting node A 220; otherwise, operation proceeds from step 214 tostep 216. In step 216, the communications device determines a networktiming reference slot time offset required to adjust said network timingto synchronize the communications network to the external timingreference signal. In some embodiments, operation proceeds from step 216to step 218. In some other embodiments, operation proceeds from step 216to connecting node A 220. Returning to step 218, in step 218 thecommunications device transmits a beacon slot start time adjustmentsignal indicating an adjustment to beacon slot timing to be made tosynchronize beacon slot timing to said external timing reference signal.Operation proceeds from step 218 to connecting node A 220. Operationproceeds from connecting node A 220 to step 222.

In step 222 the communications device operates as a master timingcontrol device. Step 222 includes step 224 in which the communicationsdevice transmits network timing reference signals, e.g., beacon signals,wherein individual transmitted network timing reference signalscommunicate a time stamp that indicates a passage of time from apreceding network timing reference signal that was transmitted by thecommunications device wherein the indicated passage of time isintentionally greater than the actual passage of time. In someembodiments, the indicated passage of time is greater than a passage oftime than could be indicated by a physical clock operating with apermitted variation of device clock speed in said communicationsnetwork. For example, WiFi specifies a maximum permitted variation andwe want to be faster than the specified maximum permitted variation interms of our artificial second indicated by successive transmittedtiming reference signals from the communications device which isoperating as a master timing reference signal. For example, ourartificial second is set to be off by 50 parts per million (ppm) in thedirection to indicate a faster clock than the real passage of time,while driving network timing toward synchronization with GPS timing.Then our artificial second is set to be off by 25 parts per million(ppm) in the direction to indicate a faster clock than the real passageof time, after network timing has synchronized with GPS timing.

Step 224 may, and in some embodiments does, include one or more of steps225 and step 226. In step 225 the communications device transmitsnetwork timing reference signals at a first rate before achievingnetwork timing synchronization with said external timing signal and at asecond rate after achieving network timing synchronization with saidexternal timing signal, wherein said first rate is higher than saidfirst rate. In one example, the first rate is 1 Hz+50 ppm, and thesecond rate is 1 Hz+25 ppm. In step 226 the communications devicetransmits network timing reference signals at a rate which varies overtime until network timing synchronization is achieved with said externaltiming reference signal. In some embodiments, including step 226,individual successive transmitted network timing reference signal,transmitted prior to achieving network timing synchronization with saidexternal timing signal, communicate a time stamp that indicates apassage of time which is intentionally greater than the actual passageof time. In some such embodiments, the passage of time indicated bysuccessive transmitted network timing reference signal before achievingnetwork timing synchronization is greater than the actual passage oftime by an amount which is larger than the amount corresponding tonetwork timing reference signals transmitted after network timingsynchronization is achieved with said external timing reference signal.For example, in one such embodiment, the communications device startsoff with treating timing periods as occurring with offset of more than25 micro-seconds, e.g., an initial offset of 50 micro-seconds and thengradually changes to 25 micro-seconds once timing synchronization isachieved with the external timing reference signal. In some embodiments,the communications device predominately uses a first timing period,e.g., with a 50 micro-second offset, prior to achieving timingsynchronization between network timing and external timing, but may andsometimes does, alter the timing period for a small fraction of the timein which the network timing is being driven to the external referencetiming, e.g., in order to more precisely align the network timing withthe external reference timing. Operation proceeds from step 222 to step228.

In step 228 the communications device monitors to detect for a loss ofsynchronization with said external timing reference signal. Step 228may, and sometimes does, include step 230 in which the communicationsdevice detects a loss of synchronization with said external timingreference signal. Operation proceeds from step 228 to step 232.

In step 232, if a loss of synchronization was not detected in themonitoring of step 228, then operation proceeds from step 228 to step222; otherwise, operation proceeds from step 228 to step 234. In step234 the communications device ceases to operate as a master timingcontrol device in response to detecting loss of synchronization withsaid external timing reference signal. Step 234 includes step 236. Instep 236 the communications device indicates a passage of time insuccessive time stamps which is closer to the actual passage of timethan is indicated while operating as a master timing control device.Operation proceeds from step 234 via connecting node B 238 to step 204.

FIG. 3 is a drawing of an exemplary communications device 300corresponding to a communications network in accordance with anexemplary embodiment. Exemplary communications device 300 is, e.g., oneof the wireless communications devices with external sourcesynchronization capability (104, 106, . . . , 108) of system 100 ofFIG. 1. Exemplary communications device 300 may, and sometimes does,implement a method in accordance with flowchart 200 of FIG. 2.

Communications device 300 includes a processor 302 and memory 304coupled together via a bus 309 over which the various elements (302,304) may interchange data and information. Communications device 300further includes an input module 306 and an output module 308 which maybe coupled to processor 302 as shown. However, in some embodiments, theinput module 306 and output module 308 are located internal to theprocessor 302. Input module 306 can receive input signals. Input module306 can, and in some embodiments does, include a wireless receiverand/or a wired or optical input interface for receiving input. Outputmodule 308 may include, and in some embodiments does include, a wirelesstransmitter and/or a wired or optical output interface for transmittingoutput. In some embodiments, memory 304 includes routines 311 anddata/information 313.

Communications device 300 includes a plurality of external timingreference source modules (external timing reference source signal module1 314, e.g., a GPS module, . . . , external timing source signal moduleN 316, e.g., a WWVB module). Each external timing reference sourcemodule, e.g., each of (314, . . . , 316) is used in receiving,processing and/or performing timing synchronization with respect aparticular type of external timing reference source outside thecommunications network, e.g., outside an ad-hoc peer to peercommunications network.

In some embodiments, processor 302 is configured to: synchronize to anexternal timing reference signal from a device outside saidcommunications network; and operate as a master timing control device,wherein operating as a master timing control device includestransmitting network timing reference signals, individual successivetransmitted network timing reference signals communicating a time stampthat indicates a passage of time from a preceding network timingreference signal that was transmitted by the communications device, saidindicated passage of time being intentionally greater than the actualpassage of time. In various embodiments, the indicated passage of timeis greater than a passage of time that could be indicated by a physicalclock operating within a permitted variation of device clock speeds insaid communication network.

In various embodiments, processor 302 is further configured to: monitorto detect network timing reference signals, prior to transmittingnetwork timing reference signals; and determine if said communicationsnetwork is synchronized to said external timing reference signal, ifnetwork timing reference signals are detected.

In some embodiments, processor 302 is further configured to: determine anetwork timing reference slot time offset required to adjust saidnetwork timing to synchronize the communications network timing to theexternal timing reference signal, when it is determined that saidnetwork is not synchronized to said external timing reference signal. Insome such embodiments, processor 302 is further configured to: transmita beacon slot start time adjustment signal indicating an adjustment tobeacon slot timing to be made to synchronize beacon slot timing to saidexternal timing reference signal.

In some embodiments, processor 302 is configured to transmit networktiming reference signals at a first rate before achieving network timingsynchronization with said external timing signal and at a second rateafter achieving network timing synchronization with said external timingsignal, wherein the first rate is higher than the second rate. In someembodiments, processor 302 is configured to transmit network timingreference signals at a rate which varies over time until network timingsynchronization is achieved with said external timing reference signal,as part of being configured to operate as a master timing controldevice. In some such embodiments, individual successive transmittednetwork timing reference signals, transmitted prior to achieving networktiming synchronization with said external timing signal, communicate atime stamp that indicates a passage of time that is intentionallygreater than an actual passage of time. In some embodiments, the passageof time indicated by successive transmitted network timing referencesignals before achieving network timing synchronization with saidexternal timing signal is greater than the actual passage of time by anamount which is larger than the amount corresponding to network timingreference signals transmitted after network timing synchronization isachieved with said external timing signal.

In some embodiments, processor 302 is further configured to: detect lossof synchronization with said external timing reference signal source;and cease to operate as a master timing control device in response todetecting loss of synchronization with said external timing referencesignal source. In some embodiments, processor 302 is configured toindicate a passage of time in successive time stamps which is closer tothe actual passage of time than is indicated while operating as a mastertiming control device, as part of being configured to cease to operateas a master timing control device.

FIG. 4 is an assembly of modules 400 which can, and in some embodimentsis, used in the exemplary wireless communications device 300 illustratedin FIG. 3. The modules in the assembly 400 can be implemented inhardware within the processor 302 of FIG. 3, e.g., as individualcircuits. Alternatively, the modules may be implemented in software andstored in the memory 304 of wireless communications device 300 shown inFIG. 3. In some such embodiments, the assembly of modules 400 isincluded in routines 311 of memory 304 of device 300 of FIG. 3. Whileshown in the FIG. 3 embodiment as a single processor, e.g., computer, itshould be appreciated that the processor 302 may be implemented as oneor more processors, e.g., computers. When implemented in software themodules include code, which when executed by the processor, configurethe processor, e.g., computer, 302 to implement the functioncorresponding to the module. In some embodiments, processor 302 isconfigured to implement each of the modules of the assembly of modules400. In embodiments where the assembly of modules 400 is stored in thememory 304, the memory 304 is a computer program product comprising acomputer readable medium, e.g., a non-transitory computer readablemedium, comprising code, e.g., individual code for each module, forcausing at least one computer, e.g., processor 302, to implement thefunctions to which the modules correspond.

Completely hardware based or completely software based modules may beused. However, it should be appreciated that any combination of softwareand hardware (e.g., circuit implemented) modules may be used toimplement the functions. As should be appreciated, the modulesillustrated in FIG. 4 control and/or configure the wirelesscommunications device 300 or elements therein such as the processor 302,to perform the functions of the corresponding steps illustrated and/ordescribed in the method of flowchart 200 of FIG. 2.

Assembly of modules 400, comprising the combination of part A 401 andpart B 403, includes a module for synchronizing to an external timingreference signal from a device outside said communications network 404,a module for monitoring to detect network timing reference signals 406,a module for determining if network timing reference signals weredetected 410, and a module for controlling operation as a function ofthe determination whether or not network timing reference signals weredetected 411. Module 406 includes a module for detecting network timingreference signals 408.

Assembly of modules 400 further includes a module for determining ifsaid communications network is synchronized to said external timingreference signal 412, a module for controlling operation as a functionof the determination as to whether or not said communications network issynchronized to said external timing reference signal 414, a module fordetermining a network timing reference slot offset required to adjustsaid network timing to synchronize the communications network to theexternal timing reference signal 416, and a module for transmitting abeacon slot time adjustment signal indicating an adjustment to thebeacon slot timing to be made to synchronize beacon slot timing to saidexternal timing reference signal.

Assembly of modules 400 further includes a module for operating as amaster timing reference device 422. Module 422 includes a module 424 fortransmitting network timing reference signals, wherein individualsuccessive transmitted network timing reference signals communicate atime stamp that indicates a passage of time from a preceding networktiming reference signal that was transmitted by the communicationsdevice where the indicated passage of time is intentionally greater thanthe actual passage of time. Module 424 includes a module fortransmitting network timing reference signals at a first rate beforeachieving network timing synchronization with said external timingreference signals and at a second rate after achieving network timingsynchronization with said external timing signal, wherein said firstrate is higher than said second rate. Module 424 also includes a modulefor transmitting network timing reference signals at a rate which variesover time until network timing synchronization is achieved with saidexternal timing reference signal 426.

Assembly of modules 400 further includes a module for monitoring todetect for a loss of synchronization with said external time referencesignal 428, a module for determining if a loss of synchronization withsaid external timing reference signal was detected 432, a modulecontrolling operation as a function of the determination if a loss ofsynchronization with said external signal was detected 433, and a modulefor ceasing to operate as a master timing control device in response todetecting loss of synchronization with said external timing referencesignal 434. Module 428 includes a module for detecting loss ofsynchronization with said external timing reference signal 430. Module434 includes a module for indicating a passage of time in successivetime stamps which is closer to the actual passage of time than isindicated while operating as a master timing control device 436.

Assembly of modules 400 further includes a module 438 for determining ifanother device in the network is already operating as a master timingcontrol device. In some embodiments, module 438 determines that a deviceis already operating as a master timing control device based on the rateof detected timing reference signals from the device, e.g., an estimatedbeacon clock rate of the device, corresponding to a predetermined value.

Various aspects and/or features of some embodiments will be furtherdiscussed below. In some embodiments, a device acts as a master in aWiFi or similar network where devices adjust their internal timing in aforward direction based on timing signals received from other deviceswithout the need for a device to expressly signal that it is acting as amaster timing control device.

In accordance with one aspect, a device first determines whether or notit should act as a timing master. The determination, in someembodiments, is based on whether or not the device has access to areliable external timing source such as a GPS signal and/or whether ornot another device is currently acting as a timing master. Whether ornot another device is acting as a timing master, in some embodiments,may be, and sometimes is, inferred from the rate at which a timingmaster transmits timing reference signals.

If a device determines that it is not to act as a timing master, itperforms synchronization based on beacon signals it receives and updatesits own timing based on the received beacon signals as necessary.

However, if a device determines that it is to act as a timing master,the device intentionally transmits using a clock rate that is fasterthan real time and, in accordance with one aspect, faster than thefastest rate expected for clocks in the system to operate at if keepingto real time. For example, in one example in one embodiment, the clockrate when operating as a timing master is controlled so that 1 second-25μsec is treated as a second rather than 1 second, where 25 μsec islarger than the normal per second clock variance expected from devicesin the system. Some other fraction of a second may be maintained but,while operating as the master, the device timing being updated at a ratewhich is faster than, but synchronized to, real time. For example, whilethe device operating as a master may update its indication of thecurrent time to indicate that a second has passed for each X secondswhere X is a fraction of a second less than 1, the update rate ismaintained in a consistent manner relative to real time. Thissynchronization may be based on synchronization to a reliable externaltiming source such as a GPS signal or some other signal. Thus, whileoperating the master device to indicate times that change at a ratewhich is faster then real time, synchronization between the devices canbe maintained based on the signals transmitted by the master devicewithout the master device expressly having to signal that it is, infact, operating as a master device.

A master device may, and in some embodiments does, relinquish its roleby simply switching back to transmitting beacon signals at a rate basedon real time rather than the accelerated understanding of time used whenoperating as a master device.

In some embodiments, another device in the system may and sometimesdoes, at any time, assume the master role by selecting and using anartificially high clock rate which is even faster than the rate in useby a device operating as a master at a given point in time.

The device operating as the timing master indicates its current time,which is based on the intentionally fast clock rate, in the beaconsignals it transmits. Devices receiving the signal operate in a normalmanner. That is, devices receiving a beacon signal from the master willdetermine that the time indicated in the received beacon signal is aheadof their own internal time and adjust their internal time and/or clockrate to synchronize to the beacon signal of the device operating as themaster.

While devices other than the device operating as the master timingdevice will transmit their understanding of time in their beaconsignals, given that their understanding of time will be behind the timeindicated by the device operating as a master, devices receiving thebeacon signals from devices operating in an ordinary manner will notalter there time based on the signals and will remain synchronized tothe device operating as a master timing control device.

In various embodiments the device operating as a master is a WiFi devicesynchronizing to a global timing source using an out of band signal, andusing this timing information for running certain applications over theWiFi channel. Exemplary timing sources that could be, and in someembodiments are used include: GPS, eLoran/LORAN-C, CDMA 2000, and WWVB.

The approach described herein allows the majority of the devices in asystem to operate in a normal manner with one or a few devicessupporting the capability of external timing synchronization andoperating as a master device in accordance with one aspect. In someembodiments, this approach doesn't require hardware changes to mostlegacy WiFi chips while allowing them to be controlled by a deviceoperating as a master control device and without requiring the legacydevices to even know that a device in the system is intentionally actingas a master timing control device.

In some embodiments enhanced WiFi capable devices use an external sourceto synchronize to a global timing reference. In some embodiments, theseenhanced devices have modified hardware in them to acquire this timinginformation. In some embodiments, after synchronizing to an externaltiming source, these enhanced devices start an adhoc network which is anenhanced network with:

One of pre-agreed names or SSIDs e.g. “Globally Synced WiFi”

One of pre-agreed beacon periods e.g. 100 ms, 1 second, 10 second

One of pre-agreed timing reference, e.g. synchronized to GPS second

Now, the legacy devices are not synchronized to the global timereference, but at a slower rate they can monitor for existence ofenhanced networks with the pre-agreed upon SSIDs. After an enhancednetwork has been discovered, the legacy devices join the network, andachieve power efficiency because of the duty cycle due to beaconperiods, and further propagate timing information to other legacydevices.

Note that each of devices using this solution would wake up at thesimilar times (up to propagation delays which should be minimal), sincethey will be synchronized indirectly to the same timing source. Thiscould enable power efficient operation for applications such as: (i)exchange of peer discovery/presence information, (ii) exchange oftraffic routing information, e.g. for multihop communication, (iii)connection setup requests, and (iv) traffic monitoring for requestsindicating intention to transmit.

Note that each of these examples are applications that the device may bedoing even if it is in the sleep mode, so an efficient implementation ofthese will significantly increase the stand by time of the device.

Drawing 500 of FIG. 5 shows one typical implementation where theexternal timing reference is the GPS second, and the beacon period isone second-25 micro-seconds, and the information being exchanged is peerdiscovery/presence information. In this case, the devices wake up everyshortened GPS second (synchronized to the GPS second), and stay awakefor a certain amount of time. This awake time could be fixed or coulddepend on the interference environment seen. If there is no activeconnection, that the device is involved in, then the device goes tosleep till the next shortened GPS second.

Note that in some embodiments, legacy devices can participate in this ifthey are in proximity, e.g., multi-hop proximity, of an enhanced device.Also, in some embodiments, the legacy device includes somefirmware/software change to configure it to listen for enhanced networkson a slow time scale, and then after discovering an enhanced network useit in an appropriate power efficient way to run various applications,e.g., various applications which would consume large amounts of powerwithout timing synchronization allowing for sleep intervals and limitedtimes of activity.

FIGS. 6-10 illustrate an example in which a wireless communicationsdevice synchronizes to an external timing reference sources and operatesas a master timing control device in accordance with an exemplaryembodiment. In drawing 600 of FIG. 6, there is a GPS satellite 602transmitting a GPS signal 614 communicating reference timinginformation, and there is a GPS coverage area 612. Drawing 600 of FIG. 6also illustrates an exemplary communications network 602, e.g., anad-hoc peer to peer network. Consider that the ad-hoc peer to peernetwork includes wireless communications device B 606, wirelesscommunications device C′ 608 and wireless communications device D′ 610.Further consider that wireless communications device A 604 has recentlyentered a coverage region of the communications network 602 and wouldlike to participate in the network. Wireless communications device A 604and wireless communications device B 606 include external sourcesynchronization capability, e.g., devices 604 and 606 can receive andprocess GPS signals and synchronize with respect to a GPS timingreference.

Device A 604 which is located within GPS coverage area 612 receives GPSsignal 614 transmitted from GPS satellite 1 602 and synchronizes to theexternal timing reference signal form the GPS satellite as indicated bybox 616.

In drawing 700 of FIG. 7, wireless communications device A 604 monitorsfor and detects network timing reference signals as indicated by box708. The detected network timing reference signals are signals (702,704, 706), e.g., beacon signals, which have been transmitted by wirelesscommunications devices (606, 608, 610), respectively. Wirelesscommunications device A 604 determines that the communications networkis not synchronized to the external timing reference signal, the GPSsignal, as indicated by block 710. Wireless communications device A 604determines a network timing reference slot, e.g., beacon slot, timeoffset required to adjust the network timing to synchronize thecommunications network to the external timing reference signals asindicated by box 712.

In drawing 800 of FIG. 8 wireless communications device A 604 operatesas a master timing control device including transmitting network timingreference signals wherein individual successive transmitted timingreference signals communicate a time stamp that indicates a passage oftime being intentionally greater than the actual passage of time, e.g.,1 second-50 micro-seconds instead of an actual passage of time of 1second. Arrow 804 represents the transmitting network timing referencesignals wherein individual successive transmitted timing referencesignals communicate a time stamp that indicates a passage of time beingintentionally greater than the actual passage of time. Signals 804 arereceived by wireless communications devices (606, 608, 610), whichsynchronize to the master timing control device timing as indicated byboxes (806, 808, 810), respectively. As wireless communications devicetransmits network timing reference signals 804 the network timing driftstoward the alignment with GPS timing as indicated by block 812.

In drawing 900 of FIG. 9 wireless communications device A 604 continuesto operate as a master timing control device. At some point in time,wireless communications device A 604 determines that network timing hasaligned to the GPS timing, e.g., based on the determined network timingreference slot offset as indicated by block 902. Then, wirelesscommunications device A 604 changes its clock rate from a clock rateused for drifting network timing to a clock rate used while networktiming is aligned with GPS timing, e.g., from 1 Hz+50 ppm to 1 Hz+25ppm, as indicated by block 904. Wireless communications device A 604continues to operate as a master timing control device includingtransmitting network timing reference signals wherein individualsuccessive transmitted timing reference signals communicate a time stampthat indicates a passage of time being intentionally greater than theactual passage of time, e.g., 1 second-25 micro-seconds instead of anactual passage of time of 1 second, as indicated by block 906. Arrow 908represents the transmitting network timing reference signals whereinindividual successive transmitted timing reference signals communicate atime stamp that indicates a passage of time being intentionally greaterthan the actual passage of time. Signals 908 are received by wirelesscommunications devices (606, 608, 610), which synchronize to the mastertiming control device timing resulting in synchronization to GPS timingas indicated by boxes (910, 912, 914), respectively.

If another device synchronized to GPS moves into network 602, the deviceentering the network 602 can immediately join and participate in thenetwork.

In drawing 1000 of FIG. 10, wireless communications device A 604 hasmoved outside the GPS coverage region 612 as indicated by dashed arrow1002. Wireless communications device A 604 detects a loss ofsynchronization with the external timing reference source, which is GPS,as indicated by block 1004. Wireless communications device A 604 ceasesto operate as a master timing control device in response to the detectedloss of synchronization with the external timing reference source asindicated by block 1006. As part of ceasing to operate as a mastertiming control device wireless communications device A 604 indicates apassage of time in successive time stamps which is closer to the actualpassage of time than is indicated while operating as a master timingcontrol device as indicated by block 1008. In one example, the passageof time indicated in the time stamps is 1 sec-2 micro-seconds based onthe tolerance of the internal clock in device A where the actual passageof time is 1 sec. Device A 604 transmits network timing signals 1010indicating a passage of time which is closer to the actual passage oftime than is indicated while operating as a master timing controldevice. If device A 604 or device B 606 moves into the GPS coverageregion, the device in the GPS coverage region may synchronize to GPS andserve as a master timing control device.

Drawing 1100 of FIG. 11 illustrates exemplary beacon period timingwithout a master timing control device in accordance with an exemplaryembodiment. Beacon signals are transmitted with a period of 1 second1108. First beacon signal 1102 communicates a time stamp of 0, secondbeacon signal 1104 communicates a time stamp of 10⁶, and third beaconsignal 1106 communicates a time stamp of 2×10⁶. Consider that timestamps represent micro seconds. In this example the indicated time inthe time stamps matches the actual passage of time.

Drawing 1200 of FIG. 12 illustrates exemplary master timing controldevice beacon period timing while driving network timing towardsynchronization with GPS timing in accordance with an exemplaryembodiment. Beacon signals are transmitted with a period of: 1 second-50micro-sec 1208. First beacon signal 1202 communicates a time stamp of 0,second beacon signal 1204 communicates a time stamp of 10⁶, and thirdbeacon signal 1206 communicates a time stamp of 2×10⁶. Consider thattime stamps represent micro seconds. In this example the indicated timein the time stamps does not match the actual passage of time. In thisexample, the time stamp for second beacon 1204 is 50 micro-secondshigher than the actual time, and the time stamp for the third beacons1206 is 100 micro-seconds higher than the actual time.

Drawing 1300 of FIG. 13 illustrates exemplary master timing controldevice beacon period timing after achieving network timingsynchronization with GPS timing in accordance with an exemplaryembodiment. Beacon signals are transmitted with a period of: 1 second-25micro-sec 1308. First beacon signal 1302 communicates a time stamp of 0,second beacon signal 1304 communicates a time stamp of 10⁶, and thirdbeacon signal 1306 communicates a time stamp of 2×10⁶. Consider thattime stamps represent micro seconds. In this example the indicated timein the time stamps does not match the actual passage of time. In thisexample, the time stamp for second beacon 1304 is 25 micro-secondshigher than the actual time, and the time stamp for the third beacons1306 is 50 micro-seconds higher than the actual time.

In some embodiments, the time stamp=(actual time−T₀)(10⁶)(Beacon rate),where T₀ is an external reference signal start time and where Beaconrate is specified in Hz. In such an embodiment, the time stamp may alsobe expressed as: time stamp=(actual time−T₀)(10⁶)/(Beacon interval),where Beacon Interval is specified in seconds. In some embodiments, theexternal reference signal is a GPS signal and T₀ is a GPS start time,e.g., the GPS epoch which is 00:00 midnight UTC on 1980-01-06. In theexample, of FIGS. 12 and 13, where a wireless communications device isoperating as a master timing control device, the beacon rate has beenartificially sped up. In various existing WiFi protocols, the fastestclock becomes the master timing control device; therefore, byartificially speeding up a clock of a device, which is alreadysynchronized to an external timing reference, the device with the spedup clock becomes the master and can synchronize network timing to theexternal timing reference.

Various embodiments are directed to achieving distributedsynchronization without any infrastructure. Various benefits fromachieving distributed synchronization include power saving and collisionavoidance between discovery messages. In some embodiments, a fraction ofthe nodes in the network are GPS connected or connected to anotherexternal timing reference source external to the communications network.In some networks the synchronization protocol, e.g., a 802.11 basedsynchronization protocol, is such that the clocks in the network aresynchronized to the fastest clock.

In various embodiments, GPS or another external timing reference sourcesuch as, e.g., CDMA, etc., provides accurate time and frequencysynchronization for some devices in the network, and is used by thosedevices to obtain synchronization to the external timing reference.However, not all the devices in the network, e.g., a peer to peer ad-hocnetwork, may have access to the external reference due to devicecapabilities and/or current device location. In various embodiments, acommunications device with the capability to synchronize to the externalsources, e.g., GPS, can co-exist with other devices and force thenetwork to converge to be synchronized to the external source timing,e.g., GPS time. In some embodiments, legacy devices in the network cansynchronize without any change to the legacy devices.

Consider that the external timing reference source is GPS. Furtherconsider an initial network without a GPS capable node. The networkfollows its own time and frequency. Further consider that a GPSconnected node joins the network. The GPS connected node would like tosynchronize the network based on the GPS timing reference. The GPSconnected node artificially speeds up its clock to be the fastest. Forexample, a 802.11 spec specifies that clocks should be 1+/−25 ppm. TheGPS connected node adopts a rate of 1+25 ppm to be the fastest clock inthe network. The adopted clock rate of 1+25 ppm may also be expressed asa time interval of 1 second-25 microseconds. In some embodiments, anynetwork that has a GPS connected node will run at the same rate, e.g.,1+25 ppm. In some embodiments, the WiFi synchronization protocolnaturally converges to the fastest clock in the network. In thisexample, the new network converges to a common global rate of 1+25 ppmwhich is not the GPS rate but is close enough to achieve the desiredpurpose.

In some embodiments, the GPS connected node is able to convert thenetwork to GPS time. The GPS connected node artificially advances timeto drift the network to GPS time. For example, the GPS connected nodeuses a faster clock when trying to correct time, e.g., 1+50 ppm. Oncetime is aligned, the GPS connected node falls back to the natural rateof 1+25 ppm. In one example, if the network is initially 500 ms off fromthe GPS second, then the GPS connected node provides a correction of 25ms each second which will take 20 seconds to convert to GPS time, afterwhich the GPS connected node will follow the standard protocol.

In various embodiments a communications device, e.g., a wirelesscommunications device (104, 106, . . . , 108) in system 100 of FIG. 1,and/or communication device 300 of FIG. 3 and/or wireless communicationsdevice 604 of FIG. 6-10 and/or wireless communications device 606 ofFIGS. 6-10 or a wireless communications device implementing beaconsignaling in accordance with FIG. 12 and/or FIG. 13 includes a modulecorresponding to each of the individual steps and/or operationsdescribed with regard to any of the Figures in the present applicationand/or described in the detailed description of the present application.In some embodiments, the modules are implemented in hardware, e.g., inthe form of circuits. Thus, in at least some embodiments the modulesmay, and sometimes are implemented in hardware. In other embodiments,the modules may, and sometimes are, implemented as software modulesincluding processor executable instructions which when executed by theprocessor of the communications device cause the device to implement thecorresponding step or operation. In still other embodiments, some or allof the modules are implemented as a combination of hardware andsoftware.

The techniques of various embodiments may be implemented using software,hardware and/or a combination of software and hardware. Variousembodiments are directed to apparatus, e.g., network nodes, mobile nodessuch as mobile terminals supporting peer to peer communications, accesspoints such as base stations, and/or communications systems. Variousembodiments are also directed to methods, e.g., method of controllingand/or operating network nodes, mobile nodes, access points such as basestations and/or communications systems, e.g., hosts. Various embodimentsare also directed to machine, e.g., computer, readable medium, e.g.,ROM, RAM, CDs, hard discs, etc., which include machine readableinstructions for controlling a machine to implement one or more steps ofa method. The computer readable medium is, e.g., non-transitory computerreadable medium.

It is understood that the specific order or hierarchy of steps in theprocesses disclosed is an example of exemplary approaches. Based upondesign preferences, it is understood that the specific order orhierarchy of steps in the processes may be rearranged while remainingwithin the scope of the present disclosure. The accompanying methodclaims present elements of the various steps in a sample order, and arenot meant to be limited to the specific order or hierarchy presented.

In various embodiments nodes described herein are implemented using oneor more modules to perform the steps corresponding to one or moremethods, for example, signal processing, signal generation and/ortransmission steps. Thus, in some embodiments various features areimplemented using modules. Such modules may be implemented usingsoftware, hardware or a combination of software and hardware. Many ofthe above described methods or method steps can be implemented usingmachine executable instructions, such as software, included in a machinereadable medium such as a memory device, e.g., RAM, floppy disk, etc. tocontrol a machine, e.g., general purpose computer with or withoutadditional hardware, to implement all or portions of the above describedmethods, e.g., in one or more nodes. Accordingly, among other things,various embodiments are directed to a machine-readable medium, e.g., anon-transitory computer readable medium, including machine executableinstructions for causing a machine, e.g., processor and associatedhardware, to perform one or more of the steps of the above-describedmethod(s). Some embodiments are directed to a device, e.g.,communications node, including a processor configured to implement one,multiple or all of the steps of one or more methods of the invention.

In some embodiments, the processor or processors, e.g., CPUs, of one ormore devices, e.g., communications nodes such as network nodes, accessnodes and/or wireless terminals, are configured to perform the steps ofthe methods described as being performed by the communications nodes.The configuration of the processor may be achieved by using one or moremodules, e.g., software modules, to control processor configurationand/or by including hardware in the processor, e.g., hardware modules,to perform the recited steps and/or control processor configuration.Accordingly, some but not all embodiments are directed to a device,e.g., communications node, with a processor which includes a modulecorresponding to each of the steps of the various described methodsperformed by the device in which the processor is included. In some butnot all embodiments a device, e.g., a communications node, includes amodule corresponding to each of the steps of the various describedmethods performed by the device in which the processor is included. Themodules may be implemented using software and/or hardware.

Some embodiments are directed to a computer program product comprising acomputer-readable medium, e.g., a non-transitory computer-readablemedium, comprising code for causing a computer, or multiple computers,to implement various functions, steps, acts and/or operations, e.g. oneor more steps described above. Depending on the embodiment, the computerprogram product can, and sometimes does, include different code for eachstep to be performed. Thus, the computer program product may, andsometimes does, include code for each individual step of a method, e.g.,a method of controlling a communications device or node. The code may bein the form of machine, e.g., computer, executable instructions storedon a computer-readable medium, e.g., a non-transitory computer-readablemedium, such as a RAM (Random Access Memory), ROM (Read Only Memory) orother type of storage device. In addition to being directed to acomputer program product, some embodiments are directed to a processorconfigured to implement one or more of the various functions, steps,acts and/or operations of one or more methods described above.Accordingly, some embodiments are directed to a processor, e.g., CPU,configured to implement some or all of the steps of the methodsdescribed herein. The processor may be for use in, e.g., acommunications device or other device described in the presentapplication.

Various embodiments are well suited to communications systems using apeer to peer signaling protocol, e.g., where direct device to devicecommunication is supported. Some embodiments use an Orthogonal FrequencyDivision Multiplexing (OFDM) based wireless peer to peer signalingprotocol, e.g., WiFi signaling protocol or another OFDM based protocol.

While described in the context of an OFDM system, at least some of themethods and apparatus of various embodiments are applicable to a widerange of communications systems including many non-OFDM and/ornon-cellular systems.

Numerous additional variations on the methods and apparatus of thevarious embodiments described above will be apparent to those skilled inthe art in view of the above description. Such variations are to beconsidered within the scope. The methods and apparatus may be, and invarious embodiments are, used with Code Division Multiple Access (CDMA),OFDM, and/or various other types of communications techniques which maybe used to provide wireless communications links between communicationsdevices. In some embodiments one or more communications devices areimplemented as access points which establish communications links withmobile nodes using OFDM and/or CDMA and/or may provide connectivity tothe internet or another network via a wired or wireless communicationslink. In various embodiments the mobile nodes are implemented asnotebook computers, personal data assistants (PDAs), or other portabledevices including receiver/transmitter circuits and logic and/orroutines, for implementing the methods.

What is claimed is:
 1. A method of operating a communications devicecorresponding to a communications network, the method comprising:synchronizing to an external timing reference signal from a deviceoutside said communications network; and operating as a master timingcontrol device, wherein operating as a master timing control deviceincludes transmitting network timing reference signals, individualsuccessive transmitted network timing reference signals communicating atime stamp that indicates a passage of time from a preceding networktiming reference signal that was transmitted by the communicationsdevice, said indicated passage of time being intentionally greater thanthe actual passage of time.
 2. The method of claim 1, furthercomprising: prior to transmitting network timing reference signals,monitoring to detect network timing reference signals; and if networktiming reference signals are detected, determining if saidcommunications network is synchronized to said external timing referencesignal.
 3. The method of claim 2, further comprising: when it isdetermined that said network is not synchronized to said external timingreference signal, determining a network timing reference slot timeoffset required to adjust said network timing to synchronize thecommunications network timing to the external timing reference signal.4. The method of claim 3, further comprising transmitting a beacon slotstart time adjustment signal indicating an adjustment to beacon slottiming to be made to synchronize beacon slot timing to said externaltiming reference signal.
 5. The method of claim 3, wherein operating asa master timing control device includes: transmitting network timingreference signals at a rate which varies over time until network timingsynchronization is achieved with said external timing reference signal.6. The method of claim 5, wherein individual successive transmittednetwork timing reference signals, transmitted prior to achieving networktiming synchronization with said external timing signal, communicate atime stamp that indicates a passage of time that is intentionallygreater than an actual passage of time.
 7. The method of claim 6,wherein the passage of time indicated by successive transmitted networktiming reference signals before achieving network timing synchronizationwith said external timing signal is greater than the actual passage oftime by an amount which is larger than the amount corresponding tonetwork timing reference signals transmitted after network timingsynchronization is achieved with said external timing signal.
 8. Themethod of claim 1, wherein said indicated passage of time is greaterthan a passage of time that could be indicated by a physical clockoperating within a permitted variation of device clock speeds in saidcommunication network.
 9. The method of claim 1, further comprising:detecting loss of synchronization with said external timing referencesignal source; and ceasing to operate as a master timing control devicein response to detecting loss of synchronization with said externaltiming reference signal source.
 10. A communications devicecorresponding to a communications network, the communications devicecomprising: means for synchronizing to an external timing referencesignal from a device outside said communications network; and means foroperating as a master timing control device including means fortransmitting network timing reference signals, wherein individualsuccessive transmitted network timing reference signals communicate atime stamp that indicates a passage of time from a preceding networktiming reference signal that was transmitted by the communicationsdevice, said indicated passage of time being intentionally greater thanthe actual passage of time.
 11. The communications device of claim 10,further comprising: means for monitoring to detect network timingreference signals, prior to transmitting network timing referencesignals; and means for determining if said communications network issynchronized to said external timing reference signal, if network timingreference signals are detected.
 12. The communications device of claim11, further comprising: means for determining a network timing referenceslot time offset required to adjust said network timing to synchronizethe communications network timing to the external timing referencesignal, when it is determined that said network is not synchronized tosaid external timing reference signal.
 13. The communications device ofclaim 12, further comprising means for transmitting a beacon slot starttime adjustment signal indicating an adjustment to beacon slot timing tobe made to synchronize beacon slot timing to said external timingreference signal.
 14. The communications device of claim 12, whereinsaid means for operating as a master timing control device includesmeans for transmitting network timing reference signals at a rate whichvaries over time until network timing synchronization is achieved withsaid external timing reference signal.
 15. A computer program productfor use in a communications device corresponding to a communicationsnetwork, the computer program product comprising: a non-transitorycomputer readable medium comprising: code for causing at least onecomputer synchronize to an external timing reference signal from adevice outside said communications network; and code for causing said atleast one processor to operate as a master timing control device,wherein said code for causing said at least one processor to operate asa master timing control device includes code for causing said at leastone processor to transmit network timing reference signals, individualsuccessive transmitted network timing reference signals communicating atime stamp that indicates a passage of time from a preceding networktiming reference signal that was transmitted by the communicationsdevice, said indicated passage of time being intentionally greater thanthe actual passage of time.
 16. A communications device corresponding toa communications network comprising: at least one processor configuredto: synchronize to an external timing reference signal from a deviceoutside said communications network; and operate as a master timingcontrol device, wherein operating as a master timing control deviceincludes transmitting network timing reference signals, individualsuccessive transmitted network timing reference signals communicating atime stamp that indicates a passage of time from a preceding networktiming reference signal that was transmitted by the communicationsdevice, said indicated passage of time being intentionally greater thanthe actual passage of time; and memory coupled to said at least oneprocessor.
 17. The communications device of claim 16, wherein said atleast one processor is further configured to: monitor to detect networktiming reference signals, prior to transmitting network timing referencesignals; and determine if said communications network is synchronized tosaid external timing reference signal, if network timing referencesignals are detected.
 18. The communications device of claim 17, whereinsaid at least one processor is further configured to: determine anetwork timing reference slot time offset required to adjust saidnetwork timing to synchronize the communications network timing to theexternal timing reference signal, when it is determined that saidnetwork is not synchronized to said external timing reference signal.19. The communications device of claim 18, wherein said at least oneprocessor is further configured to: transmit a beacon slot start timeadjustment signal indicating an adjustment to beacon slot timing to bemade to synchronize beacon slot timing to said external timing referencesignal.
 20. The communications device of claim 18, wherein said at leastone processor is configured to transmit network timing reference signalsat a rate which varies over time until network timing synchronization isachieved with said external timing reference signal, as part of beingconfigured to operate as a master timing control device.